Mutexes / Futexes

Description

CMRX offers mutual exclusive access facilities for userspace processes.

There is an implementation of futex (fast userspace mutex) available and supported. There is also an implementation of mutex (driven by kernel), but this might get deprecated anytime soon.

Data Structures
struct	futex_t
	Futex structure. More...

Macros
#define	MUTEX_INITIALIZED   1
#define	FUTEX_STATIC_INIT   { 0xFF, 0, 0 }
	Compile time initialization of futex.

Typedefs
typedef futex_t	mutex_t

Functions
int	futex_destroy (futex_t *futex)
int	futex_lock (futex_t *futex)
int	futex_unlock (futex_t *futex)
int	futex_trylock (futex_t *futex)
__SYSCALL int	mutex_init (mutex_t *restrict mutex)
	Mutexes Mutexes are fully features inter-process locking primitive.
__SYSCALL int	mutex_destroy (mutex_t *mutex)
__SYSCALL int	mutex_lock (mutex_t *mutex)
__SYSCALL int	mutex_unlock (mutex_t *mutex)
__SYSCALL int	mutex_trylock (mutex_t *mutex)
int	futex_init (futex_t *restrict futex)
	Futexes Futex is fast userspace mutex.

Macro Definition Documentation

FUTEX_STATIC_INIT

#define FUTEX_STATIC_INIT   { 0xFF, 0, 0 }

Compile time initialization of futex.

If futex is initialized using this value, then it is not necessary to call futex_init() during runtime.

MUTEX_INITIALIZED

#define MUTEX_INITIALIZED   1

Typedef Documentation

mutex_t

typedef futex_t mutex_t

Function Documentation

futex_destroy()

int futex_destroy

(

futex_t *

futex

)

futex_init()

int futex_init

(

futex_t *restrict

futex

)

Futexes Futex is fast userspace mutex.

Advantage of futex over mutex is, that it can be locked and unlocked completely from userspace. Futexes can be shared safely between threads of single process, yet can't be normally shared between threads of multiple processes unless explicitly placed into shared memory region.

futex_lock()

int futex_lock

(

futex_t *

futex

)

futex_trylock()

int futex_trylock

(

futex_t *

futex

)

futex_unlock()

int futex_unlock

(

futex_t *

futex

)

mutex_destroy()

__SYSCALL int mutex_destroy

(

mutex_t *

mutex

)

mutex_init()

__SYSCALL int mutex_init

(

mutex_t *restrict

mutex

)

Mutexes Mutexes are fully features inter-process locking primitive.

They are implemented as kernel system calls, so they are bit heavier to use than futexes. On the other hand, they can be shared accross processes.

mutex_lock()

__SYSCALL int mutex_lock

(

mutex_t *

mutex

)

mutex_trylock()

__SYSCALL int mutex_trylock

(

mutex_t *

mutex

)

mutex_unlock()

__SYSCALL int mutex_unlock

(

mutex_t *

mutex

)